Sleep apnea is a condition in which a person stops breathing for a short time while sleeping. Sleep apnea has multiple classifications based on the source of dysfunction. Obstructive sleep apnea results from mechanical blockage of the airway, for example, due to the weight of fatty neck tissue compressing the trachea. Central sleep apnea results from neurological dysfunction. Mixed sleep apnea has a combination of mechanical and neurological cause.
Symptoms of sleep apnea include snoring, breath holding during sleep, rapid awakening with gasping for air, morning headaches, depression, irritability, loss of memory, lack of energy, high risk of automobile and workplace accidents, and lack of high quality sleep and resulting daytime grogginess and sleepiness. Sleep apnea is rarely fatal but is linked to high blood pressure and increased probability of heart disease, stroke, and arrhythmias. In addition, patients with coronary artery disease who have a blood oxygen level lowered by sleep-disordered breathing may be at risk of ventricular arrhythmia and nocturnal sudden death. Sleep-disordered breathing may further cause coronary artery disease and hypertension.
There is also a high comorbidity between sleep apnea and congestive heart failure (CHF). CHF is a condition in which a weakened heart cannot pump enough blood to body organs. Heart failure may affect either the right side, left side, or both sides of the heart. As pumping action is lost, blood may back up into other areas of the body, including the liver, gastrointestinal tract, and extremities (right-sided heart failure), or the lungs (left-sided heart failure). Structural or functional causes of heart failure include high blood pressure (hypertension), valvular heart disease, congenital heart diseases, cardiomyopathy, heart tumor, and other heart diseases. Precipitating factors include infections with high fever or complicated infections, use of negative inotropic drugs (such as beta-blockers and calcium channel blocker), anemia, irregular heartbeats (arrhythmias), hyperthyroidism, and kidney disease.
Various treatments exist for sleep apnea including medical device treatments, surgery, and drugs. The type of treatment depends on the type of sleep apnea. For patients with implantable pacemakers, another treatment for sleep apnea is pacing therapy, which is currently being used for treating heart conditions. The use of pacing therapy for sleep apnea is still relatively unexplored. Hence, there is a continuing need to improve the techniques for applying pacing therapy from implantable cardiac devices in a manner that effectively combats sleep apnea.